The objectives of this project broadly stated are to conduct complementary field and laboratory investigations of Schistosoma japonicum infections with emphasis on immune phenomena which might be correlated with clinical disease states. We propose to monitor antibody and cell mediated immune response including possibly significant associated phenomena in selected population groups living in an area where Schistosoma japonicum is highly endemic. Attempts will be made to correlate these observations with parasitologic and clinical data, with notes of fluctuation of changes over an extended period, and to assess if possible the degree to which the immune phenomena contribute directly to the pathology of the disease. Attempts will be made to assess immunologically the acquisition of infection in children in the endemic area. In addition, the effect of chemotherapy on immune response and an immunological assessment at the effect of chemotherapy will be investigated. These studies are being carried out as a cooperative program with the Philippine Department of Health with field studies on the islands of Luzon, Samar, Leyte, The Philippines.